You have checked with your health professionals and they're not worried - so you don't need to worry. Small bubbies are fine, just as large bubbies are. Make sure you've got some 5 zero and 4 zero clothes just in case and start thinking happy thoughts about your impending DD. She's going to be petite and beautiful. Not long now!

P.S Do you know the error margin for measuring babies size is something ridiculous like 40%?